Medical catheters having a balloon mounted thereon are useful in a variety of medical procedures. Balloon catheters may be used to widen a vessel into which the catheter is inserted by dilating the blocked vessel, such as in an angioplasty procedure. Balloon catheters may also be used to expand and/or seat a medical device such as a stent or graft at a desired position within a body lumen. In all of these applications, fluid under pressure may be supplied to the balloon through an inflation lumen in the catheter, thereby expanding the balloon.
It is essential in the manufacture of balloon catheters to properly seal the balloon to the catheter. The seal must be able to withstand the high pressures to which it is subjected on inflation of the balloon. A poor seal may result in leakage of inflation fluid and inability to achieve the desired pressure or even rapid loss of pressure and deflation of the balloon.
A number of methods for sealing a balloon to a catheter are known in the art. Methods involving the use of a suitable adhesive to bond the balloon to the catheter tube are described in U.S. Pat. No. 4,913,701 and U.S. Pat. No. 4,943,278. The use of adhesives, however, adds to the thickness of the catheter and increase its rigidity at the region of the bonds.
Another such method, where heat fusible materials are employed, involves the application of heat to fuse the balloon to the catheter tube. To that end, resistance heating of copper jaws has been employed to fuse a balloon to a catheter tube. Resistance heating, however, can result in the formation of small, random channels at the balloon-catheter interface, potentially giving rise to undesirable variations in the strength of different bonds. Such heating can also cause undesirable crystallization and stiffening of the balloon and catheter material, not only at the bond site, but also in both directions axially of the bond, due to heat conduction through the balloon and the catheter, and heat radiation from the jaws.
A non-contact method for heat sealing a balloon onto a catheter is disclosed in U.S. Pat. No. 4,251,305 to Becker et al. A length of thin tubing is slid over an elongated shaft of the catheter and shrink tubing installed over the thin walled tubing at its ends overlapping the catheter shaft. The shrink tubing is partially shrunk. Lamps emitting energy along the visible and infrared spectra are used to provide radiant energy to form thermoplastic joints that bond the tubing and shaft. This method, nevertheless, suffers from the problem of undesired heat transfer along the catheter and balloon.
Yet another fusion-based method disclosed in U.S. Pat No. 5,501,759 to Forman involves the use of a beam of laser radiation to match an absorption characteristic of polymeric materials. The polymeric materials are melted by the radiation and then allowed to cool and solidify to form a fusion bond.
Another fusion-based method described in Forman involves the simultaneous use of multiple beams of energy to supply energy at discrete points about the circumference of the balloon and thereby heat the balloon. A single beam can be split into multiple beams and the multiple beams directed about the circumference of the balloon via fiber optics.
In many prior methods of manufacturing catheter assemblies, an example of which is illustrated in PRIOR ART FIG. 1, joint formation is accomplished by overlapping (e.g. a lap weld configuration) the components 1 and 2 to be joined on a mandrel 3 and heating a region of the overlapping components to form a weld or joint 4. Because the components are typically cylindrical in shape (or at least in the regions where they are to be joined) and inherently have differing diameters to accommodate their overlap, the components tend to form a space 5 therebetween. Such a space presents difficulties in maintaining proper and continuous engagement between the components during joint formation. To address this, a heat shrink 6 or other constricting device is thus used to force the components 1 and 2 together during heating. Where the components 1 and 2 are a catheter shaft and a balloon waist, typically the joint 4 is about 1 mm in length. To prevent inadvertent heating and possible damage to the balloon cone 6, approximately 0.5 mm of the waist 2 immediately adjacent to the cone 6 remains un-welded. This unjoined region of the catheter/balloon interface may contribute to joint failure during expansion of the balloon under pressure and present difficulties during the folding process.
In addition to the above, it is also noted that such prior manufacturing methods, also tend to provide a rather abrupt transition between the balloon and catheter shaft which may affect catheter flexibility, trackability, and/or cross-over performance of the resulting catheter assembly.
Thus, a need exists to provide a catheter with joints that not only are adequately sealed and resistant to bond failure, but which do not deter the overall performance of the catheter. A method of manufacturing such a catheter is also needed.
All US patents and applications and all other published documents mentioned anywhere in this application are incorporated herein by reference in their entirety.
Without limiting the scope of the invention a brief summary of some of the claimed embodiments of the invention is set forth below. Additional details of the summarized embodiments of the invention and/or additional embodiments of the invention may be found in the Detailed Description of the Invention below.
A brief abstract of the technical disclosure in the specification is provided as well only for the purposes of complying with 37 C.F.R. 1.72. The abstract is not intended to be used for interpreting the scope of the claims.